Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals (e.g. cellphones, tablet computers and other electronic devices). Each wireless terminal communicates with one or more base stations via transmissions on one or more uplinks and downlinks. A downlink (or forward link) refers to the communication link from the base stations to the wireless terminal, and an uplink (or reverse link) refers to the communication link from the wireless terminal to the base station. These communication links may be established via a single-in-single-out (SISO), multiple-in-single-out (MISO), or a multiple-in-multiple-out (MIMO) system.
A MIMO system employs multiple transmit antennas and multiple receive antennas for data transmission. A MIMO channel formed by the transmit and receive antennas may be decomposed into independent channels, which are also referred to as spatial channels. Each of the independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensions created by the multiple transmit and receive antennas are utilized.
A MIMO system supports time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the uplink and downlink transmissions are within the same frequency region so that the reciprocity principle allows the estimation of the downlink channel from the uplink channel. This enables the base station to extract transmit beamforming gain on the downlink when multiple antennas are available at the base station.
The primary purpose of the base station is to provide connectivity between a wireless terminal or terminals and the core communications network. In a UMTS radio access network (RAN), the functionalities of a base station may be split across two network elements: the Radio Network Controller (RNC) handles, among other functions, connection setup, resource assignment and mobility; the base node (NodeB) configured to handle the radio transmission and reception to and from wireless terminals as well as the resource allocation for connected users on the shared channels.
To establish a call connection between a wireless terminal and a base station, a Radio Access Bearer (RAB) is needed. The RAB carries voice or other data between the wireless terminal and the core communication network. When packets are transmitted across a wireless network, it may be necessary for the receiving device to send acknowledgement messages to the sender. Once an acknowledgement message is received by a wireless terminal, that message may no longer be retransmitted by the wireless terminal.
A wireless terminal may determine the receive status of previously transmitted messages from a receiver. A poll request may be sent from the wireless terminal to the intended receiver. In response, the intended receiver may send a message to the wireless terminal indicating a list of received and not received messages. Currently, the poll request provides an opportunity to send a PDU to the intended receiver. Currently, this opportunity is typically used to send the most recently transmitted PDU to the intended receiver. However, this may not realize the full potential retransmission benefit when sending a poll. Accordingly, there is an opportunity to improve the utility of retransmission polling on wireless networks.